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如果我有一個帶有單個骨骼的幾何體，我可以使用動畫來渲染它，但是如果它有2個骨骼，頂點不會正確動畫，我會加載從blender導出的JSON格式，據我瞭解子骨骼相對矩陣乘以它的父絕對矩陣，然後乘以相對矩陣的逆矩陣，然後每個骨骼矩陣乘以關鍵幀矩陣以得到最終矩陣，然後將這些矩陣發送到頂點着色器。 我將體重和骨骼指數設置爲VBO的屬性。Android OpenGL ES2骨骼動畫子骨骼矩陣
for (int y = 0; y < g.getBones().size(); y++) {
com.thatulborooj.opengl.objects.Bone bone = new com.thatulborooj.opengl.objects.Bone();
Bone gBone = g.getBones().get(y);
float[] t = new float[] { gBone.getPosition().get(0), gBone.getPosition().get(0), gBone.getPosition().get(0) };
float[] r = new float[] { gBone.getRotation().get(0), gBone.getRotation().get(1), gBone.getRotation().get(2), gBone.getRotation().get(3) };
float[] s = gBone.getScale() == null ? new float[] { 1, 1, 1 } : new float[] { gBone.getScale().get(0), gBone.getScale().get(1), gBone.getScale().get(2) };
float[] nMatrix = createMat4(t, r, s);
float[] inverseMatrix = new float[16];
if (gBone.getParent() == -1) {
bone.setBindMatrix(nMatrix);
invertM(inverseMatrix, 0, nMatrix, 0);
float[] fMatrix = new float[16];
multiplyMM(fMatrix, 0, nMatrix, 0, inverseMatrix, 0);
bone.setFinalMatrix(fMatrix);
} else {
float[] pMatrix = mesh.getBones().get(gBone.getParent()).getBindMatrix();
float[] bMatrix = new float[16];
multiplyMM(bMatrix, 0, pMatrix, 0, nMatrix, 0);
bone.setBindMatrix(bMatrix);
invertM(inverseMatrix, 0, bMatrix, 0);
float[] fMatrix = new float[16];
multiplyMM(fMatrix, 0, bMatrix, 0, inverseMatrix, 0);
bone.setFinalMatrix(fMatrix);
}
bone.setName(gBone.getName());
bone.setParent(gBone.getParent());
mesh.getBones().add(bone);
}
}
這是渲染代碼
if (animated) {
if (playing) {
if (curFrame < frames) {
for (int i = 0; i < bones.size(); i++) {
Key key = animations.get(0).getHierarchy().get(i).getKeys().get(curFrame);
setIdentityM(aMatrix, 0);
multiplyMM(aMatrix, 0, bones.get(i).getFinalMatrix(), 0, key.getMatrix(), 0);
for (int q = 0; q < 16; q++) {
bs[i][q] = aMatrix[q];
}
}
curFrame++;
} else
curFrame = 0;
shaderProgram.setBones(bs);
}
}
這是使從位置，四元數和分的基體中的功能：
public static float[] createMat4(float[] t, float[] r, float[] s) {
float[] mat4 = new float[16];
float[] T = new float[16];
float[] R = quaternionToMatrix(r);
float[] S = new float[16];
setIdentityM(T, 0);
setIdentityM(S, 0);
translateM(T, 0, t[0], t[1], t[2]);
scaleM(S, 0, s[0], s[1], s[2]);
float[] temp = new float[16];
multiplyMM(temp, 0, T, 0, R, 0);
multiplyMM(mat4, 0, temp, 0, S, 0);
return mat4;
}
private static float[] quaternionToMatrix(float[] q) {
float[] m = new float[16];
final float xx = q[0] * q[0];
final float xy = q[0] * q[1];
final float xz = q[0] * q[2];
final float xw = q[0] * q[3];
final float yy = q[1] * q[1];
final float yz = q[1] * q[2];
final float yw = q[1] * q[3];
final float zz = q[2] * q[2];
final float zw = q[2] * q[3];
// Set matrix from quaternion
m[0] = 1 - 2 * (yy + zz);
m[1] = 2 * (xy - zw);
m[2] = 2 * (xz + yw);
m[3] = 0;
m[4] = 2 * (xy + zw);
m[5] = 1 - 2 * (xx + zz);
m[6] = 2 * (yz - xw);
m[7] = 0;
m[8] = 2 * (xz - yw);
m[9] = 2 * (yz + xw);
m[10] = 1 - 2 * (xx + yy);
m[11] = 0;
m[12] = 0;
m[13] = 0;
m[14] = 0;
m[15] = 1;
return m;
}
我通過此線設置的骨頭陣列均勻：
private void setBonesUniforms() {
for (int i = 0; i < bones.length; i++) {
int uBonesLocation = glGetUniformLocation(program, "bones[" + i + "]");
glUniformMatrix4fv(uBonesLocation, 1, false, bones[i], 0);
}
}
終於這是頂點着色器：
vec4 newVertex=vertexPosition;
vec4 newNormal=vertexNormal;
if(animated==1){
int index;
index=int(skinindex.x);
newVertex = (bones[index] * skinweight.x) * vertexPosition;
newNormal = (bones[index] * skinweight.x) * vertexNormal;
index=int(skinindex.y);
newVertex += (bones[index] * skinweight.y) * vertexPosition;
newNormal += (bones[index] * skinweight.y) * vertexNormal;
}
newVertex=vec4(newVertex.xyz, 1.0);
我注意到用任何浮點數更改子骨骼矩陣不會改變結果。